Genes a, b, and c are known to be in that linear order in an organism. A testcross is done that yields 20 double crossover progeny out of a total of 1000 offspring. Assume that there is no interference.

(a) Type a genetic map showing the distances between these genes. Is there more than one possible map?
(b) What would the distances be if there was 10% interference?
(c) What number of double crossover progeny would be expected if there was interference of 15%?

Explanation:

The observed frequency of the double crossovers (DCOs) is 20/1000, or 0.02. If there is no interference then this will be the same as the expected, which is just the product of the single crossover frequencies, that is, SCO frequency (a-b) x SCO freq. (b-c) = 0.02.

(a) Any combination of map distances whose product (a-b) x (b-c) = 0.02 is possible. However, three are most likely:

a 20 mu b 10 mu c

a 10 mu b 20 mu c

a 14.14 mu b 14.14 mu c

(b) The distances would be exactly the same.

(c) The expected number of DCO progeny would be 17.

loss of sensation to pressure and touch

the dorsal column–medial lemniscus pathway (dcml) (also known as the posterior column-medial lemniscus pathway (pcml)) is a sensory pathway of the central nervous system that conveys sensations of fine touch, vibration, two-point discrimination, and proprioception (position) from the skin and joints.

the two new cells are called daughter cells